As the micronization of an LSI (large scale integration) device progresses, accurate measurement of a resultant product obtained by the manufacturing process becomes necessary. This is because an accurate result in accordance with the degree of micronization is demanded in the manufacturing process, and the determination therefor requires the accurate measurement. It is also because the result of the above accurate measurement is used in the feedback for the accuracy of the manufacturing process, the management of the manufacturing process, or the management of the performance of the LSI device obtained by the manufacturing process, for example. In the manufacturing process, therefore, the measurement of the result obtained by the manufacturing process is necessary, and the measurement requires accuracy. However, while the measurement relating to the planar structure of the LSI device (e.g., the length measurement of the width of a photoresist) is usually performed immediately, the measurement relating to the cross-sectional structure, such as the length measurement of a gate oxide film in the growth process thereof, the length measurement of a shallow trench isolation film in the growth process thereof, and the length measurement of a diffusion preventing film for preventing the diffusion of a metal from a metal wiring in the growth process thereof, for example, has not been performed to measure the result of the manufacturing process immediately and accurately in the manufacturing process.
Meanwhile, as means for observing the cross-sectional microstructure, a TEM (Transmission Electron microscope) apparatus is usually used which includes a unit for irradiating an electron beam, an electron lens used to guide electrons transmitted through a sample or electrons scattered by the sample to a detector, a diaphragm for adjusting the amount of the electron beam, and a transmitted electron detection unit for detecting the transmitted electron beam.
In the observation of the sample by the above TEM apparatus, the amount of electrons to be guided to the transmitted electron detection unit has been determined by the electron lens, with the opening of the diaphragm fixed.
In the TEM apparatus according to the conventional example 1, however, the structure of a semiconductor detector which serves also as the diaphragm for the transmitted electron detector is designed to be the structure of a diaphragm/semiconductor detector illustrated in FIG. 1, to thereby make the opening of the diaphragm/semiconductor detector variable and thus limit the passage of unintended scatted electrons from the diaphragm/semiconductor detector. Accordingly, improvement is observed in an electron diffraction image obtained by the TEM apparatus after the transmission of electrons through the sample (Patent Document 1: Japanese Unexamined Patent Application Publication No. 6-139988).
The diaphragm/semiconductor detector illustrated in FIG. 1 includes a semiconductor detector 1, a fixing pin 2, a lever pin 4, a guide hole 3, a rotary ring 5, a board 6, and a shaft 7. When the rotary ring 5 is rotated by the shaft 7, the semiconductor detector 1 moves along the guide hole 3 and rotates around the fixing pin 2. As a result, the diameter of a central hole formed by a plurality of the semiconductor detectors 1 changes. Thereby, the amount of electrons directed to a transmitted electron detector placed behind the semiconductor detectors 1 is adjusted. Accordingly, with the transmitted electron detector and the semiconductor detector 1, a dark-field or bright-field electron diffraction image in accordance with the amounts of electrons captured by the respective detectors can be obtained.
Meanwhile, in a TEM apparatus according to the second conventional example 2, a diaphragm for a transmission detector has an opening of a plurality of sizes, and thus the amount of electrons passing through the diaphragm can be adjusted. As a result, improvement is observed in an electron diffraction image obtained by the TEM apparatus after the transmission of electrons through a sample (Patent Document 2: Japanese Unexamined Patent Application Publication No. 5-217536).
The diaphragm of the TEM apparatus according to the conventional example 2 is herein illustrated in FIG. 2. The diaphragm of FIG. 2 includes a lower diaphragm plate 133 having a plurality of opening sets each including openings of four sizes, an upper diaphragm plate 130 having one of the above opening sets, a lower retaining mechanism 134 for the lower diaphragm plate 133, an upper retaining mechanism 131 for the upper diaphragm plate 130, lower diaphragm holes 136 included in the lower diaphragm plate 133, and upper diaphragm holes 132 included in the upper diaphragm plate 130. Thus, the amount of electrons of an electron beam 135 can be adjusted by the upper diaphragm plate 130 and then further by the lower diaphragm plate 133. Furthermore, the electron beam 135 can be further narrowed to an arbitrary amount by slightly displacing the upper diaphragm plate 130 and the lower diaphragm plate 133 from each other.
The above apparatus, however, has not been used in the manufacturing process as means for immediately and accurately measuring the result obtained by the manufacturing process.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 6-139988    Patent Document 2: Japanese Unexamined Patent Application Publication No. 5-217536